Original Research ARTICLE
Predicting the dielectric response of saturated sandstones using a 2-electrode measuring system
- 1Deltares, Netherlands
- 2Delft University of Technology, Netherlands
4-electrode setups are usually used to measure the dielectric response (complex conductivity)of sandstones, as it is known that 2-electrode systems are sensitive to unwantedelectrode polarization at low frequency. Moreover, electrode polarization (EP) occurs inthe frequency range where the characteristic relaxation associated to the grain size also occurs, which can therefore theoretically be assessed using 4-electrode setups. Nonetheless, we find that other parameters of interest (porosity, salinity) can easily be extracted from the frequency range 1 - 10 kHz, beyond the one affected by EP using a 2 electrode setup. An additional unwanted effect (”pseudo-inductance”) is observed in the frequency range 10 kHz - 1 MHz during our experiments. Even though the origin of this effect remains unknown, it is shown to be correlated with the ionic strength of the system and the electrode separation. The bulk polarization region, i.e. the region of intermediate frequencies devoid of EP and pseudo-inductance polarizations, is the one of interest, as the complex conductivity of the system is there only dependent on material parameters such as the porosity of the sandstone and the conductivity of the electrolyte. We demonstrate that in the bulk region the model predicts the complex conductivity response, when these porosity and ionic strength are known. The model has been validated using laboratory measurements on a Bentheim sandstone saturated with five different NaCl concentrations: 5 mM, 10 mM, 100 mM, 170 mM and 540 mM.
Keywords: Dielectric Spectroscopy, sandstone, Electrode polarization, impedance, 2-electrode setup
Received: 24 Oct 2018;
Accepted: 05 Dec 2018.
Edited by:Dick Bedeaux, Norwegian University of Science and Technology, Norway
Reviewed by:Miguel Rubi, University of Barcelona, Spain
Siddharth S. Gautam, The Ohio State University, United States
Copyright: © 2018 Kirichek, Chassagne and Ghose. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Dr. Alex Kirichek, Deltares, Delft, 2600, Netherlands, Netherlands, Alex.Kirichek@deltares.nl